Advantages of a Technology for the Hydride Pickling of High-Alloy Steels and Alloys

Abstract

Results obtained from use of the hydride method to pickle more than 90 grades of steel showed that this technology is very effective. Its effectiveness is due to the following factors:

• the high productivity of lines designed for the pickling of stainless steels;

• a decrease in the amount of metal lost during the pickling operation;

• the formation of a higher-quality surface on the product compared to oxidative pickling and the elimination of over-pickling, point corrosion, and the diffusion of hydrogen into the steel;

• a 25% reduction in costs due to the changeover of the hydride pickling bath to gas heating;

• a significant reduction in acid consumption;

• an increase in the service life of the equipment in the pickling department;

• an improvement in environmental conditions, since the absence of hexavalent chromium and nitrates in the waste water makes it easier to clean; there is also a sharp reduction in the amount of slime that is formed, and the release of harmful vapors is curtailed because the acid baths are heated to lower temperatures than in the standard technology.

Hydride pickling technology can be further improved in the course of its use on lines built to pickle strip, sheet, and wire. Recent advances provide for cold plastic deformation of the material before pickling. The degree of deformation is chosen so that the residual plastic strain in the surface layer is within the range 0.3–0.6%.